update,

it114105/itp4510/Assignment/22-23/LinkedList.java

@@ -0,0 +1,193 @@
+class ListNode {
+
+	private Object data;
+	private ListNode next;
+
+	public ListNode(Object o) { data = o; next = null; }
+	public ListNode(Object o, ListNode nextNode)
+		{ data = o; next = nextNode; }
+
+	public Object getData() { return data; }
+	public void setData(Object o) { data = o; }
+	
+	public ListNode getNext() { return next; }
+	public void setNext(ListNode next) { this.next = next; }
+
+
+} // class ListNode
+
+class EmptyListException extends RuntimeException {
+	public EmptyListException ()
+		{ super("List is empty"); }
+} // class EmptyListException
+
+public class LinkedList {
+
+	private ListNode head;
+	private ListNode tail;
+
+	private int length;		// the length of the list
+
+	public LinkedList() {
+		head = tail = null;
+		length = 0;
+	}
+
+	public boolean isEmpty() { return head == null; }
+
+	public void addToHead(Object item) {
+		if (isEmpty())
+			head = tail = new ListNode(item);
+		else
+			head = new ListNode(item, head);
+		length++;
+	}
+
+	public void addToTail(Object item) {
+		if (isEmpty())
+			head = tail = new ListNode(item);
+		else {
+			tail.setNext(new ListNode(item));
+			tail = tail.getNext();
+		}
+		length++;
+	}
+
+	public Object removeFromHead() throws EmptyListException {
+		Object item = null;
+		if (isEmpty())
+			throw new EmptyListException();
+		item = head.getData();
+		if (head == tail)
+			head = tail = null;
+		else
+			head = head.getNext();
+		length--;
+		return item;
+	}
+
+	public Object removeFromTail() throws EmptyListException {
+		Object item = null;
+		if (isEmpty())
+			throw new EmptyListException();
+		item = tail.getData();
+		if (head == tail)
+			head = tail = null;
+		else {
+			ListNode current = head;
+			while (current.getNext() != tail)
+				current = current.getNext();
+			tail = current;
+			current.setNext(null);
+		}
+		length--;
+		return item;
+	}
+	
+	public int count() {
+		return length;
+	}
+	
+	// students need to revise toString method
+	public String toString() {
+		String str = "";
+		ListNode current = head;
+		while (current != null) {
+			FoodOrder foodOrder = (FoodOrder) current.getData();
+			str += foodOrder + "\n";
+			current = current.getNext();
+		}
+		return str;
+	}
+
+	 
+	/**
+
+	Removes a ListNode from the LinkedList with a specific Member ID.
+
+	@param targetID the Member ID of the ListNode to be removed
+
+	@throws EmptyListException if the list is empty
+	*/
+	public void remove(int targetID) throws EmptyListException {
+
+		// Throw an exception if the list is empty
+		if (isEmpty()) {
+			throw new EmptyListException();
+		}
+		
+		// If the target node is the head node, remove it from the head
+		if (((FoodOrder) head.getData()).getMemberID() == targetID) {
+			removeFromHead();
+			return;
+		}
+		
+		// Traverse the linked list to find the target node
+		ListNode current = head.getNext();
+		ListNode prev = head;
+		
+		while (current != null && ((FoodOrder) current.getData()).getMemberID() != targetID) {
+			prev = current;
+			current = current.getNext();
+		}
+		
+		// If the target node is found, remove it
+		if (current != null) {
+			prev.setNext(current.getNext());
+			length--;
+		}
+	}
+
+	/**
+
+	Checks if the linked list contains a FoodOrder object with the given targetID as its member ID.
+	@param targetID the member ID to search for in the linked list
+	@return true if the linked list contains a FoodOrder object with the given targetID as its member ID, false otherwise
+	*/
+	public boolean contain(int targetID) {
+		ListNode current = head;
+		while (current != null) {
+			if (((FoodOrder) current.getData()).getMemberID() == targetID) {
+				return true;
+			}
+			current = current.getNext();
+		}
+		return false;
+	}
+	
+	/**
+
+	Adds a new FoodOrder to the LinkedList in the correct position based on its priority.
+	@param item the FoodOrder to add to the LinkedList
+	*/
+	public void add(Object item) {
+		FoodOrder foodOrderItem = (FoodOrder) item;
+	
+		// if the list is empty, add the new node as the head
+		if (isEmpty()) 
+			addToHead(item);
+		
+		// if the new node has higher priority than the head, add it as the new head
+		else if (foodOrderItem.getPriority() < ((FoodOrder) head.getData()).getPriority()) 
+			addToHead(item);
+		
+		// if the new node has lower priority than the tail, add it as the new tail
+		else if (foodOrderItem.getPriority() >= ((FoodOrder) tail.getData()).getPriority()) 
+			addToTail(item);
+		
+		// otherwise, find the correct position for the new node and insert it
+		else {
+			ListNode current = head.getNext();
+			ListNode prev = head;
+	
+			while (current != null && foodOrderItem.getPriority() >= ((FoodOrder) current.getData()).getPriority()) {
+				prev = current;
+				current = current.getNext();
+			}
+	
+			prev.setNext(new ListNode(item, current));
+			length++;
+		}
+	}
+	
+}